Stop and lock for a vertically storing dock leveler

ABSTRACT

A dock leveler with a pivotal deck includes a stop mechanism that provides the deck with a positive stop at the deck&#39;s vertically stored position without the deck&#39;s actuator having to be fully extended. With the actuator being less than fully extended, the stop mechanism and actuator can exert opposing forces that help prevent the deck from rocking back and forth as the deck settles to its stationary, upright position. In some cases, the stop mechanism is part of a combination stop-and-lock mechanism that includes a locking device for temporary providing a redundant or alternate lock that prevents the deck from descending unexpectedly while the dock leveler is being serviced or repaired.

FIELD OF THE DISCLOSURE

The present disclosure generally pertains to dock levelers with avertically storing deck and more specifically to a stop-and-lockmechanism for the deck.

BACKGROUND OF RELATED ART

A typical loading dock of a building includes an exterior doorway withan elevated platform for loading and unloading vehicles, such as trucksand trailers. To compensate for height differences between the loadingdock platform and an adjacent bed of a truck or trailer, many loadingdocks have a dock leveler. A typical dock leveler includes a deck orramp that is pivotally hinged along its back edge to vary the height ofits front edge. An extension plate or lip extends outward from thedeck's front edge to span the gap between the rear of the truck bed andthe front edge of the deck. This allows personnel and material handlingequipment to readily move on and off the vehicle during loading andunloading operations.

The deck is usually moveable between a stored position and an operativeposition. Depending on the style of dock leveler, the deck may storeeither vertically or horizontally. U.S. Pat. No. 6,502,268 shows anexample of a horizontally storing deck, and U.S. Pat. No. 5,396,676discloses a dock leveler with a vertically storing deck.

Vertically storing decks are usually driven by a hydraulic cylinder. Thehydraulic cylinder typically extends to raise the deck to its verticallystored position and retracts as the deck descends to its operativeposition. The force for lowering the deck can come from the hydraulicaction within the cylinder and/or the weight of the deck itself. In somecases, the deck's weight urges the deck downward while a hydraulic flowrestriction associated with the cylinder provides the deck withcontrolled descent.

The hydraulic cylinder can also be used for holding the pivotal deck atits vertically stored position. A pivotal anchor point of the cylinder,the pivotal anchor point of the deck, and the pivotal connection betweenthe deck and the cylinder can be positioned so that the deck is verticalwhen the cylinder's piston rod bottoms out (i.e., the piston rod fullyextends to the end of its stroke). When stopping and holding the deck inthis manner, however, the radial pin clearance at the various pivotalconnections allows the deck to rock back and forth before the decksettles to a completely stationary, upright position.

The temporary rocking motion may exert undo stresses and/or wear at thepin joints and related components. Moreover, when servicing or repairingthe dock leveler, it may be desirable to have a redundant or morepositive locking mechanism for holding the deck upright.

Consequently, a need exists for a better stop and/or locking mechanismfor holding a dock leveler's deck at a vertically stored position andselectively securing it for service and repair work.

SUMMARY

In some embodiments, a vertically storing dock leveler includes a stopmechanism that provides a pivotal deck with a positive stop at thedeck's vertically stored position without the deck's actuator having tobe fully extended.

In some embodiments, a vertically storing dock leveler includes acombination stop-and-lock mechanism that provides a positive stop at thedeck's vertically stored position and provides a redundant lock thatprevents the deck from descending unexpectedly.

In some embodiments, the combination stop-and-lock mechanism includes athreaded connection for infinite adjustment of the deck's verticallystored position.

In some embodiments, a dock leveler includes a lock mechanism that canbe selectively locked and unlocked by simply inserting or removing ablocking pin.

In some embodiments, a stop-and-lock mechanism provides relative slidingmotion between itself and a pivotal deck. The relative sliding motionallows the deck and part of the stop-and-lock mechanism to pivot abouttwo different axes.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view of a dock leveler with its deck in a stored,upright position plus a schematic view a hydraulic system coupled to thedock leveler.

FIG. 2 is a side view of the dock leveler of FIG. 1 but showing the deckin a lowered, operative position.

FIG. 3 is a side view similar to FIGS. 1 and 2 but showing the deck inan intermediate position.

FIG. 4 is a perspective view of a stop mechanism and a lock mechanismused with the dock leveler of FIGS. 1-3.

DETAILED DESCRIPTION

FIGS. 1-3 illustrate a vertically storing dock leveler 10 installed at aloading dock 12 of a building 14. Dock leveler 10 includes a deckstructure 16 that provides a variably inclined or level traffic surface18 upon which material handling equipment and dockworkers can travelbetween a trailer bed 20 of a vehicle 22 and an elevated platform 24within the building. The equivalent terms, “deck” and “deck structure”refer to those parts of the dock leveler that are substantiallystationary relative to the pivotal traffic surface 18. In other words,deck structure 16 and traffic surface 18 generally move as one.

Deck 16 can pivot about a rear axis 26 so that an actuator 28 canposition and hold deck 16 to a stored upright position (FIG. 1), variouslowered operative positions (FIG. 2), and at an intermediate position(FIG. 3). Actuator 28 represent any powered device (e.g., single-actinghydraulic cylinder, double-acting hydraulic cylinder, pneumaticcylinder, rodless cylinder, inflatable bladder, rack-and-pinion, leadscrew, hydraulic motor, electric motor, pneumatic motor, etc.) that canraise and/or lower the front end of a dock leveler's deck, such as frontend 30 of deck 16. In one example, actuator 28 comprises a double-actingcylinder 32, a piston 34 and a piston rod 36. A distal end 38 of pistonrod 36 is pinned to deck 16, and a cylinder end 40 is pinned forrotation about a stationary axis 42.

In this particular example, actuator 28 (double-acting cylinder 32) ispowered by a hydraulic system 41 comprising conventional hydrauliccontrol valves and a pump. The hydraulic valves are used for selectivelypressurizing, trapping, and releasing hydraulic fluid in a first line 43and a second line 45, wherein first line 43 leads to a cylinder end 40of actuator 28 and second line 45 leads to a rod end 44. The pressure inlines 43 and 45 help determine the movement of deck 16.

To lower deck 16 from its stored upright position of FIG. 1 to itsoperative position of FIG. 2, hydraulic system 41 pressurizes rod end 44via line 45 and controllably releases the hydraulic fluid withincylinder end 40 via line 43. This allows piston 34 and rod 36 to retractwithin cylinder 32. Due to the deck's weight, the pressure differentialacross piston 34, and the radial offset between the deck's pivotal axis26 and the cylinder's pivotal axis 42, deck 16 pivots downward asactuator 28 retracts. Hydraulic system 41 may release the pressure incylinder end 40 in a controlled manner so that deck 16 descends at acontrolled rate.

To raise deck 16 from its operative position of FIG. 2 to its storedposition of FIG. 1, hydraulic system 41 deliver hydraulic pressure tocylinder end 40 via line 43 and releases pressure from rod end 44 vialine 45. The hydraulic pressure at cylinder end 40 acts upon piston 34to urge actuator 28 from its retracted position (FIG. 2) toward a fullyextended position. The fully extended position of actuator 28 is whenpiston 34 reaches its rated travel limit 46 at rod end 44 of cylinder 32(assuming actuator 28 was entirely removed from dock leveler 10 and iscompletely free to extend). FIG. 1 shows piston 34 having stopped justshort of limit 46, thus distance 48 represents the additional distancepiston 34 would need to travel in order for actuator 28 to be at itsfully extended position.

Since piston 34 has more distance to travel before bottoming out at therod end of cylinder 32, as shown in FIG. 1, actuator 28 can continueurging deck 16 to pivot beyond the stored upright position. The phrase,“pivot beyond the stored upright position,” refers to the deck travelingaway from the upright position in an area that is outside the range thatlies between the operative position and the vertically stored position.To prevent deck 16 from pivoting beyond the stored upright position, astop mechanism 50 external to cylinder 32 mechanically stops deck 16 atits stored upright position. As actuator 28 continues urging deck 16 tomove beyond its vertical position, stop mechanism 50 prevents suchmovement. Thus, actuator 28 and stop mechanism 50 exert opposing forcesthat can firmly hold deck 16 at its vertically stored position. At thispoint, hydraulic system 41 can de-energize its pump and actuate itsvalves to releasably trap hydraulic fluid in at least line 43, wherebythe trapped fluid can hold deck 16 steady at its stored uprightposition.

Although the actual design of stop mechanism 50 may vary, in oneexample, stop mechanism 50 comprises a rod 52 that a pin 54 couples to astationary frame member 56 of dock leveler 10. Pin 54 allows rod 52 topivot about an axis 58 that is vertically and/or horizontally offset toaxis 26 of deck 16. The offset distance between axes 26 and 58 causesrelative sliding motion between rod 52 and a fixed arm 60 of deck 16.Arm 60 includes a plate 62 with an oblong hole 64 through which rod 52extends. As deck 16 and arm 60 pivot about axis 26, rod 52 pivots aboutaxis 58 and slides axially within hole 64. The oblong shape of hole 64prevents rod 52 from binding within hole 64 as rod 52 tilts relative todeck 16. As deck 16 pivots toward its stored upright position, a head 66on rod 52 eventually engages plate 62 (FIGS. 1 and 4) which limitsfurther movement between rod 52 and plate 62 and thus stops the deck'supward pivotal motion at the deck's stored upright position.

To provide stop mechanism 50 with an adjustable feature that can varythe exact location at which deck 16 stops, the position of head 66 onrod 52 can be axially adjustable via a threaded connection between head66 and rod 52 or by some other means. Head 66, for example, can be aninternally threaded nut 68 that screws onto external threads on rod 52.Once properly adjusted, a second nut 70 can be tightened against nut 68to hold nut 68 in place. In lieu of second nut 70, nut 68 could be of aself-locking nut or some other conventional thread locking mechanism,compound or method could be used.

In addition to actuator 28 holding deck 16 at its stored uprightposition, a lock mechanism 72 (FIG. 4) can be added to provide aredundant or alternative lock that prevents deck 16 from descendingunexpectedly while servicing or repairing dock leveler 10. In oneexample, lock mechanism 72 is incorporated in the structure of stopmechanism 50, thereby creating a combination stop-and-lock mechanism 74.Lock mechanism 72, for instance, can be a removable blocking pin 76 thatcan be temporarily inserted into a hole 80 in rod 52 such that arm 60becomes trapped between pin 76 and nut 68, thereby inhibiting relativesliding movement between rod 52 and arm 60.

Although the invention is described with respect to various examples,modifications thereto will be apparent to those of ordinary skill in theart. The scope of the invention, therefore, is to be determined byreference to the following claims:

1. A dock leveler for facilitating the loading or unloading of a vehicleat a loading dock, the dock leveler comprising: a deck structure pivotalbetween a stored upright position and a lowered operative position; anactuator having a retracted position and a fully extended position, theactuator is coupled to the deck structure such that the actuator pivotsthe deck structure from the lowered operative position to the storedupright position in response to the actuator moving toward the fullyextended position; and a stop mechanism engaging the deck structure whenthe deck structure is in the stored upright position, wherein the stopmechanism prevents the actuator from reaching the fully extendedposition when the deck structure is at the stored upright position. 2.The dock leveler of claim 1, further comprising an adjustable feature onthe stop mechanism, wherein the adjustable feature can be manipulated tovary the stored upright position.
 3. The dock leveler of claim 2,wherein the adjustable feature includes a threaded connection.
 4. Thedock leveler of claim 1, wherein the stop mechanism includes a lockmechanism that selectively couples the stop mechanism to the deckstructure to mechanically hold the deck structure at substantially thestored upright position.
 5. The dock leveler of claim 4, wherein thelock mechanism includes a pin that selectively engages and disengagesthe stop mechanism thereby respectively coupling and uncoupling the stopmechanism and the deck structure.
 6. The dock leveler of claim 1,wherein the deck structure pivots about a first axis, and the stopmechanism pivots about a second axis, wherein the first axis and thesecond axis are spaced apart from each other.
 7. The dock leveler ofclaim 1, wherein the stop mechanism and the deck structure define asliding connection therebetween.
 8. The dock leveler of claim 1, whereinthe actuator comprises a piston and a cylinder.
 9. A dock leveler forfacilitating the loading or unloading of a vehicle at a loading dock,the dock leveler comprising: a deck structure pivotal between a storedupright position and a lowered operative position; an actuator having aretracted position and a fully extended position, the actuator iscoupled to the deck structure such that the actuator pivots the deckstructure from the lowered operative position to the stored uprightposition in response to the actuator moving toward the fully extendedposition; and a combination stop-and-lock mechanism interactivelycoupled to the deck structure, the combination stop-and-lock mechanismis selectively configured in a locked state and an unlocked state suchthat the stop-and-lock mechanism limits the deck structure's movementtoward the lowered operative position when the stop-and-lock mechanismis in the locked state, the stop-and-lock mechanism allows the deckstructure's movement toward the lowered operative position when thestop-and-lock mechanism is in the unlocked state, the stop-and-lockmechanism prevents the actuator from reaching the fully extendedposition when the deck structure is at the stored upright position. 10.The dock leveler of claim 9, further comprising an adjustable feature onthe stop-and-lock mechanism, wherein the adjustable feature can bemanipulated to vary the stored upright position.
 11. The dock leveler ofclaim 10, wherein the adjustable feature includes a threaded connection.12. The dock leveler of claim 11, wherein the stop-and-lock mechanismincludes a pin that can be selectively engaged and disengaged.
 13. Thedock leveler of claim 9, wherein the deck structure pivots about a firstaxis, and part of the stop-and-lock mechanism pivots about a secondaxis, wherein the first axis and the second axis are spaced apart fromeach other.
 14. The dock leveler of claim 9, wherein the stop-and-lockmechanism and the deck structure define a sliding connectiontherebetween.
 15. The dock leveler of claim 9, wherein the actuatorcomprises a piston and cylinder.
 16. A method of operating a dockleveler that includes a deck structure that is pivotal between a storedupright position and a lowered operative position, a hydraulic cylinderthat is extendable from a retracted position toward a fully extendedposition to raise the deck structure from the lowered operative positionto the stored upright position, and a hydraulic system with a first linecoupled to a cylinder-end of the hydraulic cylinder and perhaps a secondline coupled to the rod-end of the cylinder, the hydraulic system can becontrolled for selectively pressurizing, trapping, and releasinghydraulic fluid in the first line and the second line, the methodcomprising: pressurizing the hydraulic fluid in the first line to extendthe hydraulic cylinder and raise the deck structure from the loweredoperative position to the stored upright position; and mechanicallystopping the deck structure at the stored upright position before thehydraulic cylinder reaches the fully extended position.
 17. The methodof claim 16, further comprising: after the step of mechanically stoppingthe deck structure at the stored upright position, discontinuing thestep of pressurizing the hydraulic fluid in the first line; andreleasably trapping the hydraulic fluid in the first line to inhibit thedeck structure from returning to the lowered operative position.
 18. Themethod of claim 17, further comprising: after the step of releasablytrapping the hydraulic fluid in the first line, pressurizing the secondline to urge the deck structure from the stored upright position towardthe lowered operative position.
 19. The method of claim 18, furthercomprising: while pressurizing the second line, controllably releasingthe hydraulic fluid from within the cylinder via the first line tocontrollably lower the deck structure from the stored upright positiontoward the lowered operative position.
 20. The method of claim 16,further comprising: mechanically holding the deck structure at thestored upright position while depressurizing the hydraulic fluid in thefirst line.
 21. The method of claim 17, further comprising: after thestep of releasably trapping the hydraulic fluid in the first line,controllably releasing the hydraulic fluid in the first line andmanually urging the deck structure from the stored upright positiontoward the lowered operative position.